I don't think you can go wrong with any of them. We stayed in the Finding Nemo suites and loved it! We looked out onto the kiddie pool next to the Big Blue pool and it was delightful! No noise complaints. Easy walk in the morning for coffee and easy walk to the buses.
We stayed at The Lion King suites in October and really enjoyed it. We are looking to stay in the Finding Nemo Suites our next trip only because DD1 is a huge Nemo fan. I don't think you could go wrong with any of the 3. That being said I find Nemo seems to fill up faster probably since its closer to the Big Blue Pool and the main building.
My wife and daughter and I just came back from a 5 night stay this week and had stayed in the Little Mermaid room. If we go back to AoA in the future (we want to stay at some other resorts too), we'd most likely go with the Nemo section since it's centrally located. Cars or Lion King wouldn't be bad...but Nemo is literally right there next to the pool and cafeteria.
But as others have said...they are all well themed, so you can't go wrong with any of them!
We've stayed in a LK suite twice so far and loved the location. It's quiet, yet still close to everything. We always request a room close to transportation and both times we had rooms right at the end of the building closest to Animation Hall. That meant we had less than a 100 yard walk from our room to the food court (which is important to us since we use the refillable mugs a lot) and just a few steps further to the Big Blue pool. The bus stops were a quick walk through the main building or by walking through the LK building and then along the parking lot when we were in building 10. The most important thing for us is to be close to the bus stops and food court as we use both of those things at least a few times a day. We usually only go swimming 2 or 3 times during the week so it's not a big deal for us to have to walk to a pool.
We're heading back to AoA this summer but we're staying in a Nemo suite this time for 2 reasons: 1) We want to try something different -- the original plan was to stay at POFQ, but that didn't happen because... 2) Other family members who are traveling with us for this trip will be staying at Pop Century so we figured the Nemo suites would be the best location for this stay since we will probably be walking back and forth between the two resorts more often than we usually do. I'm already slightly dreading staying in a Nemo suite since I know that chances are pretty good that wherever our room is (other than the front section of building 5) will be a longer walk to the food court and bus stops than our LK suites were....but I'm sure we'll be fine...we're just spoiled by the locations of our LK suites.
All that being said, I think all of the sections are great and wouldn't be upset with any of them (though I think being in Building 2 of the Cars section might make me a little cranky). Cars is by far my favorite at night and I make it a point to walk over there at least one night during our stay.